Ooi Nuke Plant: KEPCO Waited 10 Hours Before Announcing the Alarm and Leak, with NISA's Approval

Certain things will never change, nuclear accident or not.

From Jiji Tsushin (6/21/2012):

警報出ればすぐ公表＝大飯原発、遅れ批判で－保安院
Responding to the criticism in delay in announcement regarding Ooi Nuke Plant, NISA says if an alarm sounds it will be promptly announced

　再稼働の準備が進む関西電力大飯原発３号機（福井県おおい町）で、発電機冷却系の警報の公表が遅れた問題で、経済産業省原子力安全・保安院は２１日、「予期されていない警報などが出た場合は、安全への影響にかかわらず速やかに公表する」とのルールを決めた。

About the delay in announcing the alarm at the generator cooling system of Reactor 3 at Kepco's Ooi Nuclear Power Plant which is being prepared for the restart, the Nuclear and Industrial Safety Agency under METI decided on a new rule on June 21 that "if an unexpected alarm sounds, it will be promptly announced regardless of the effect on safety".

　大飯原発では１９日午後９時５０分ごろ、発電機冷却系のタンク水位低下を示す警報が鳴ったが、関電は安全上の影響はないとして、保安院の了解を得た上で１０時間以上たった翌２０日朝に公表した。

At Ooi Nuclear Power Plant, an alarm sounded at about 9:50PM on June 19 indicating the water level decreased in the tank of the generator cooling system. KEPCO decided that there was no effect on safety, and obtaining the consent from the NISA to do so announced the event in the morning of June 20, more than 10 hours after the event.

There was also a leak at the pump in the cooling system at Reactor 3 on June 19, and KEPCO also waited until June 20 to announce. According to Sankei Shinbun (6/21/2012):

関西電力は２０日、大飯原子力発電所３号機（おおい町）で、発電機を冷やす水をタンクから送り出すポンプの一部から、わずかに水漏れしていたと発表した。前日１９日夜のタンクの水位低下には影響なく、環境への影響はなかった。

KEPCO announced on June 20 that there was a slight leak of water from the part of the pump that transfers water from the generator cooling system tank. [According to KEPCO,] the leak had no effect on the water level decrease in the tank on the night of June 19, and there was no effect on the environment.

　関電によると、１９日午後１０時ごろ、水位低下が見つかった同３号機の発電機の冷却水タンク周辺を調べている際、現場作業員が微量の水漏れを発見したとしている。

According to KEPCO, a worker was inspecting the area around the generator cooling system tank of Reactor 3 at about 10PM on June 19, when he noticed a minute amount of leak.

　水漏れは、ポンプの部品を通った水に含まれる不純物を除去するチューブ部分。

The water leak was from the tube that removes foreign matters in the water running through the pump.

　関電は、チューブ接続部のボルトを締め、交換も検討している。

KEPCO has tighten the bolt at the connection of the tube, and is considering replacing it.

According to KEPCO's press release, the leak was 0.02cc/second. The press release has a PDF file with a diagram of the system, but it is hard for me to figure out what is what. The location of the leak is not immediately clear, and there is no photograph of the actual leak. It looks KEPCO needs to learn a little bit from TEPCO when it comes to communicating with the outside world. TEPCO's communication skills have improved over the past year under the unfortunate circumstance.

(I don't want to be too familiar with a pressurized water reactor. I don't want to do a self-inflicted crash course on one, like I did on the boiling water reactors in Fukushima as they blew up. Don't start Ooi Nuke Plant. I don't have time to learn a new reactor type. I don't want to even learn about a turbine generator. Don't do it. Learning a little about Mitsubishi's steam generators is already too much...)

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San Onofre Nuke Plant: Faulty Steam Generator Was Made by Mitsubishi Heavy Industries

The plant operator replaced all the steam generators at the plant in December 2010 with the steam generators (SG) made by Mitsubishi Heavy Industries. Unit 3 re-started in February 2011. Unit 2 is under regular maintenance.

From The Orange County Register (2/2/2012):

As workers began inspecting a leaky tube in one of the San Onofre nuclear plant's reactors Thursday, federal regulators said more than 800 tubes in a second, offline reactor showed wear and thinning, although they are less than two years old.

And plant officials confirmed that sensors showed a tiny amount of radioactive gas may have leaked out of a building next to the first reactor before the reactor was shut down late Tuesday.

All four of the plant's steam generators and their tubes are less than two years old, installed after being delivered to the West Coast by the Japanese manufacturer of the generators, Mitsubishi Heavy Industries.

Some 9,700 tubes carry water from the reactor and through each generator.

"They have inspected 80 percent of the tubes in one of the steam generators at unit 2," said Victor Dricks, spokesman for the Nuclear Regulatory Commission. "Two of the tubes have thinning so extensive that they need to be plugged and taken out of service. Sixty nine other tubes have thinning greater than 20 percent of the wall thickness, and a larger number have thinning greater than 10 percent of wall thickness."

The tubes with 10 percent thinning number more than 800, he said.

Gil Alexander, a spokesman for plant operator Southern California Edison, said he could not confirm Dricks's numbers Thursday because an assessment of the unit 2 tubes is continuing.

Dricks and Alexander, however, said that highly sensitive alarms were tripped in an building next to San Onofre's unit 3 reactor after the leak was detected about 5:30 p.m. Tuesday, indicating that at least some radioactive gas was present.

The building houses the turbine that generates electricity.

...

And while workers were able to begin inspecting the unit 3 reactor, which had cooled enough to allow them to enter, they had not yet been able to characterize the size or nature of the leak, he said.

Mitsubishi officials were on scene, he said, and he had no estimate of when the reactor might be started up again, though it will likely be several days.

“Mitsubishi is aware of the issue reported at the San Onofre Nuclear Generating Station and has been in contact with the customer, Southern California Edison," the company said in a statement released to the press. "The investigation of the incident is being conducted by our customer. However, as the manufacturer of the steam generators, we will do whatever we can to support our customer in resolving the issue.”

New details also emerged about an unrelated accident on Friday, when a contract worker slipped into a pool above the unit 2 reactor, now offline for maintenance, while trying to retrieve a flashlight.

The man, whose name Edison declined to release, was not injured, and did not suffer harmful radiation exposure, but might have ingested the mildly radioactive water, Alexander said. No internal contamination was found.

Normally, water that is heated by the reactor and flows through the tubes is kept separate from another loop of water, from another source, inside the steam generators.

Instead, the tubes are immersed in the water inside the steam generators, heating the water, which turns to steam that powers the plant's turbines to produce electricity.

But a small leak in one of the tubes could have allowed radioactive water circulating from the reactor to mix with the water in the steam generator.

If so, it could have resulted in the escape of a small amount of radioactive gas.

(Full article at the link)

From Enformable (2/2/2012):

It’s not clear what caused the pipe to fail, or whether the company was facing an isolated break in a single alloy tube or a manufacturing defect that might be at issue elsewhere in the massive plant tube system.

This might mean there is a now a worry about the possibility that San Onofre has purchased 4 faulty steam generators from Mitsubishi, and the financial costs to replace them might prevent the plant from restarting.

Southern California Edison said a manufacturing defect was reported by Mitsubishi before delivery of two generators from Japan — but that the equipment was retested by the manufacturer and plant operator and determined to be fine before installation at the southern reactor.

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California's San Onofre's Leak Was 30 Gallons/Hr

Oh and the low level of radioactive gas may also have leaked.

30 gallons of water per hour = 113 liters of water per hour.

From Emformable (2/1/2012), citing the NRC event notification:

MANUAL TRIP DUE TO A PRIMARY TO SECONDARY LEAK GREATER THAN 30 GAL/HR

“At 1505 PST, Unit 3 entered Abnormal Operation Instruction S023-13-14 ‘Reactor Coolant Leak’ for a steam generator leak exceeding 5 gallons per day.

“At 1549 PST, the leak rate was determined to be 82 gallons per day. At 1610 PST, a leak rate greater than 75 gallons per day with an increasing rate of leakage exceeding 30 gallons per hour was established and entry into S023-13-28 ‘Rapid Power Reduction’ was performed.

“At 1630 PST, commenced rapid power reduction per S023-13-28 ‘Rapid Power Reduction’. At 1731 PST, with reactor power at 35% the Unit was manually tripped. At 1738 PST, Unit 3 entered Emergency Operation Instruction S023-12-4 ‘Steam Generator Tube Rupture’.

“At 1800 PST the affected steam generator was isolated.”

All control rods fully inserted on the trip. Decay heat is being removed thru the main steam bypass valves into the main condenser. Main feedwater is maintaining steam generator level. No relief valves lifted during the manual trip. The plant is in normal shutdown electrical lineup.

Unit 2 is presently in a refueling outage and was not affected by this event.

The licensee has notified the NRC Resident Inspector. The licensee has issued a press release.

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